How to merge a transparent PNG image with another image using PIL?

This article discusses how to put a transparent PNG image with another image. This is a very common operation on images. It has a lot of different applications. For example, adding a watermark or logo on an image. To do this, we are using the PIL module in Python. In which we use some inbuilt methods and combine the images in such a way that it looks to be pasted.

• Open Function - It is used to open an image.
• Convert Function - It returns a converted copy of a given image. It converts the image to its true color with a transparency mask.
• Paste Function - It is used to paste an image on another image. 

Syntax: PIL.Image.Image.paste(image_1, image_2, box=None, mask=None)
OR 
image_object.paste(image_2, box=None, mask=None)

Parameters:

• image_1/image_object : It is the image on which other image is to be pasted.
• image_2: Source image or pixel value (integer or tuple).
• box: An optional 4-tuple giving the region to paste into. If a 2-tuple is used instead, it’s treated as the upper left corner. If omitted or None, the source is pasted into the upper left corner.
• mask: a mask that will be used to paste the image. If you pass an image with transparency, then the alpha channel is used as the mask.

Approach:

• Open the front and background image using Image.open() function.
• Convert both the image to RGBA.
• Calculate the position where you want to paste the image.
• Use the paste function to merge the two images.
• Save the image.

Input Data:

To input the data, we are using two images:

• Front Image: A transparent image like a logo

• Background image: For background like any wallpaper image

Implementation:

# import PIL module
from PIL import Image

# Front Image
filename = 'front.png'

# Back Image
filename1 = 'back.jpg'

# Open Front Image
frontImage = Image.open(filename)

# Open Background Image
background = Image.open(filename1)

# Convert image to RGBA
frontImage = frontImage.convert("RGBA")

# Convert image to RGBA
background = background.convert("RGBA")

# Calculate width to be at the center
width = (background.width - frontImage.width) // 2

# Calculate height to be at the center
height = (background.height - frontImage.height) // 2

# Paste the frontImage at (width, height)
background.paste(frontImage, (width, height), frontImage)

# Save this image
background.save("new.png", format="png")

Output: